Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of an image carrier; an optical writer emits a light beam onto the charged surface of the image carrier to form an electrostatic latent image on the image carrier according to the image data; a development device supplies toner to the electrostatic latent image formed on the image carrier to make the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image carrier onto a recording medium or is indirectly transferred from the image carrier onto a recording medium via an intermediate transfer member; a cleaner then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
The fixing device used in such image forming apparatuses may employ a fixing roller and a pressing roller that apply heat and pressure to the recording medium bearing the toner image. For example, the pressing roller is pressed against the fixing roller heated by a heater to form a fixing nip therebetween through which the recording medium bearing the toner image is conveyed. As the fixing roller and the pressing roller rotating in the recording medium conveyance direction convey the recording medium through the fixing nip, the fixing roller heated by the heater and the pressing roller apply heat and pressure to the recording medium, melting and fixing the toner image on the recording medium.
During the fixing operation described above, toner may adhere to the outer circumferential surface of the pressing roller from the toner image on the recording medium and remain there even after the fixing operation. In order to remove the residual toner, a web made of a nonwoven fabric impregnated with silicone oil contacts the outer circumferential surface of the pressing roller. The web is supplied from a supply reel and taken up by a take-up reel. For example, as the take-up reel pulls the web from the supply reel, the web stretched between the take-up reel and the supply reel moves slowly and slides over the outer circumferential surface of the pressing roller, thus wiping the residual toner off the pressing roller.
However, if the recording medium is jammed at the fixing nip, a user may rotate the pressing roller in the direction counter to the recording medium conveyance direction to pick up the jammed recording medium from between the fixing roller and the pressing roller. Accordingly, the pressing roller rotating in the direction counter to the recording medium conveyance direction may pull the redundant web from the supply reel, producing slack in the web. Consequently, the slackened web may be entangled or skewed, resulting in faulty conveyance of the web and faulty cleaning of the pressing roller.
To address this problem, a brake mechanism that brakes the moving web is proposed. For example, the brake mechanism includes a pad separatably pressed against the web by a cam. When the cam presses the pad against the web, the pad minimizes movement of the web, preventing slack in the web. However, the brake mechanism has the complex structure that upsizes the fixing device and increases manufacturing costs.
Alternatively, a method for taking up the web after the user removes the jammed recording medium is proposed. For example, after the user removes the jammed recording medium, the take-up reel takes up the web a plurality of times while the fixing roller and the pressing roller are rotated for a predetermined time, unreeling the fresh web and cleaning the pressing roller precisely with the fresh web.
Although effective for its intended purpose, this method has a drawback in that if the user rotates the pressing roller accidentally even when no recording medium is jammed between the fixing roller and the pressing roller, and therefore the pressing roller pulls the redundant web from the supply reel, this method may not activate because it is configured to activate solely after removal of the jammed recording medium. Accordingly, slack in the redundant web may not be eliminated, resulting in faulty conveyance of the web and faulty cleaning of the pressing roller.